Brome mosaic virus (BMV) is a member of the alphavirus-like superfamily and is a plant-infecting, (+)-strand RNA virus. BMV RNA replication occurs entirely in the cytoplasm of infected cells and requires 2 virally-encoded proteins and several host factors. Studies of BMV and related viruses indicate that RNA replication occurs in association with cytoplasmic membranes and that specialized virus-induced cytoplasmic vesicles are likely involved. We are using electron microscopy to characterize further the subcellular localization and makeup of these specialized vesicles. Cryofixation techniques will prove useful in these studies to help in the preservation of membrane ultrastructure. We hope to characterize virus-induced vesicles in both barley protoplasts, the natural host of BMV, and also in Saccharomyces cerevisia, a genetically tractable system in which BMV replicates.